He told reporters in Warsaw that developed nations should make good on pledges made in 2010 and immediately pay the promised $30bn to help poor countries cope with the effects of climate change.

Rich countries also need to clarify how they intend to scale that up to $100bn per year by 2020, he said.

"That would be a very important starting point and key to the successful conclusion of the negotiation of a [post-]2020 agreement," said Su.

Delegates from nearly 200 nations are in the Polish capital for 11-22 November negotiations on a new global climate treaty.

Countries are aiming to reach agreement by 2015 on a pact to succeed the Kyoto Protocol that would set binding caps on their greenhouse gas emissions after 2020.

But few countries have committed to firm emission reduction targets, while major developing nations such as China and India, which have no caps under Kyoto, insist that success is predicated on rich governments coughing up more cash.

"We want to see a very clear roadmap ... we want to see the actual and real provision of financial sources," said Su.

The issue of climate finance is at the forefront of the UN talks after the Philippines and parts of southeast Asia were ravaged this week by typhoon Haiyan, one of the most powerful storms ever recorded.

Japan dismays

"We are firmly committed to the mandate we agreed to [at 2011 UN talks] in Durban that the parties would take enhanced action after 2020," Su said, offering no more details.

China's veteran negotiator would not comment on when China will announce its own post-2020 emissions reduction targets.

China has promised to reduce its emissions per unit of economic output to 40-45% below 2005 levels by 2020.

Su also criticised developed nations for doing too little to step up efforts to reduce their emissions.

Asked about reports that Japan will weaken its emissions target, Su said he had "no way of describing my dismay".

Japan in 2009 pledged to cut greenhouse gases by 25% below 1990 levels by 2020. But the country is expected to this week lower that target to a 3% increase over the same period, local media reported last month, citing no sources.

Su said that the European Union's goal to slash emissions by 20% between 1990 and 2020 was so unambitious that it would "certainly be over-achieved".

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